在基于flyway java的迁移中不会注入Spring bean

Question

我正在尝试在flyway迁移java代码中注入配置属性的组件，但它总是为null。

我正和Flyway一起使用弹簧靴。

@Component
@ConfigurationProperties(prefix = "code")
public class CodesProp {

    private String codePath;
 }

然后在Flyway迁移代码中，尝试按照以下方式自动执行此组件：

public class V1_4__Migrate_codes_metadata implements SpringJdbcMigration {

@Autowired
private CodesProp codesProp ;
public void migrate(JdbcTemplate jdbcTemplate) throws Exception {
    codesProp.getCodePath();  
}

这里，codesProp始终为空。

有没有办法在flyway中注入spring bean或者在flyway bean之前初始化它？

谢谢。

Answer 1

Flyway不支持向SpringJdbcMigration实施中的依赖注入。它只是在类路径上查找实现SpringJdbcMigration的类，并使用默认构造函数创建一个新实例。这是在SpringJdbcMigrationResolver中执行的。执行迁移后，SpringJdbcMigrationExecutor会创建一个新的JdbcTemplate，然后调用迁移实施的migrate方法。

如果您确实需要将依赖项注入到基于Java的迁移中，我认为您必须实现自己的MigrationResolver，它从应用程序上下文中检索特定类型的bean并创建并返回每个ResolvedMigration个实例。

Answer 2

如果像我一样，您不想等待Flyway 4.1，您可以使用Flyway 4.0并将以下内容添加到Spring Boot应用程序中：

1）在项目中创建一个ApplicationContextAwareSpringJdbcMigrationResolver类：

import org.flywaydb.core.api.FlywayException;
import org.flywaydb.core.api.MigrationType;
import org.flywaydb.core.api.MigrationVersion;
import org.flywaydb.core.api.configuration.FlywayConfiguration;
import org.flywaydb.core.api.migration.MigrationChecksumProvider;
import org.flywaydb.core.api.migration.MigrationInfoProvider;
import org.flywaydb.core.api.migration.spring.SpringJdbcMigration;
import org.flywaydb.core.api.resolver.ResolvedMigration;
import org.flywaydb.core.internal.resolver.MigrationInfoHelper;
import org.flywaydb.core.internal.resolver.ResolvedMigrationComparator;
import org.flywaydb.core.internal.resolver.ResolvedMigrationImpl;
import org.flywaydb.core.internal.resolver.spring.SpringJdbcMigrationExecutor;
import org.flywaydb.core.internal.resolver.spring.SpringJdbcMigrationResolver;
import org.flywaydb.core.internal.util.ClassUtils;
import org.flywaydb.core.internal.util.Location;
import org.flywaydb.core.internal.util.Pair;
import org.flywaydb.core.internal.util.StringUtils;
import org.flywaydb.core.internal.util.scanner.Scanner;
import org.springframework.context.ApplicationContext;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Map;

/**
 * Migration resolver for {@link SpringJdbcMigration}s which are registered in the given {@link ApplicationContext}.
 * This resolver provides the ability to use other beans registered in the {@link ApplicationContext} and reference
 * them via Spring's dependency injection facility inside the {@link SpringJdbcMigration}s.
 */
public class ApplicationContextAwareSpringJdbcMigrationResolver extends SpringJdbcMigrationResolver {

    private final ApplicationContext applicationContext;

    public ApplicationContextAwareSpringJdbcMigrationResolver(Scanner scanner, Location location, FlywayConfiguration configuration, ApplicationContext applicationContext) {
        super(scanner, location, configuration);
        this.applicationContext = applicationContext;
    }

    @SuppressWarnings("unchecked")
    @Override
    public Collection<ResolvedMigration> resolveMigrations() {
        // get all beans of type SpringJdbcMigration from the application context
        Map<String, SpringJdbcMigration> springJdbcMigrationBeans =
                (Map<String, SpringJdbcMigration>) this.applicationContext.getBeansOfType(SpringJdbcMigration.class);

        ArrayList<ResolvedMigration> resolvedMigrations = new ArrayList<ResolvedMigration>();

        // resolve the migration and populate it with the migration info
        for (SpringJdbcMigration springJdbcMigrationBean : springJdbcMigrationBeans.values()) {
            ResolvedMigrationImpl resolvedMigration = extractMigrationInfo(springJdbcMigrationBean);
            resolvedMigration.setPhysicalLocation(ClassUtils.getLocationOnDisk(springJdbcMigrationBean.getClass()));
            resolvedMigration.setExecutor(new SpringJdbcMigrationExecutor(springJdbcMigrationBean));

            resolvedMigrations.add(resolvedMigration);
        }

        Collections.sort(resolvedMigrations, new ResolvedMigrationComparator());
        return resolvedMigrations;
    }

    ResolvedMigrationImpl extractMigrationInfo(SpringJdbcMigration springJdbcMigration) {
        Integer checksum = null;
        if (springJdbcMigration instanceof MigrationChecksumProvider) {
            MigrationChecksumProvider version = (MigrationChecksumProvider) springJdbcMigration;
            checksum = version.getChecksum();
        }

        String description;
        MigrationVersion version1;
        if (springJdbcMigration instanceof MigrationInfoProvider) {
            MigrationInfoProvider resolvedMigration = (MigrationInfoProvider) springJdbcMigration;
            version1 = resolvedMigration.getVersion();
            description = resolvedMigration.getDescription();
            if (!StringUtils.hasText(description)) {
                throw new FlywayException("Missing description for migration " + version1);
            }
        } else {
            String resolvedMigration1 = ClassUtils.getShortName(springJdbcMigration.getClass());
            if (!resolvedMigration1.startsWith("V") && !resolvedMigration1.startsWith("R")) {
                throw new FlywayException("Invalid Jdbc migration class name: " + springJdbcMigration.getClass()
                                                                                                     .getName() + " => ensure it starts with V or R," + " or implement org.flywaydb.core.api.migration.MigrationInfoProvider for non-default naming");
            }

            String prefix = resolvedMigration1.substring(0, 1);
            Pair info = MigrationInfoHelper.extractVersionAndDescription(resolvedMigration1, prefix, "__", "");
            version1 = (MigrationVersion) info.getLeft();
            description = (String) info.getRight();
        }

        ResolvedMigrationImpl resolvedMigration2 = new ResolvedMigrationImpl();
        resolvedMigration2.setVersion(version1);
        resolvedMigration2.setDescription(description);
        resolvedMigration2.setScript(springJdbcMigration.getClass().getName());
        resolvedMigration2.setChecksum(checksum);
        resolvedMigration2.setType(MigrationType.SPRING_JDBC);
        return resolvedMigration2;
    }
}

2）添加一个新的配置类来对Spring Boot生成的Flyway实例进行后期处理：

import org.flywaydb.core.Flyway;
import org.flywaydb.core.internal.dbsupport.DbSupport;
import org.flywaydb.core.internal.dbsupport.h2.H2DbSupport;
import org.flywaydb.core.internal.dbsupport.mysql.MySQLDbSupport;
import com.pegusapps.zebra.infrastructure.repository.flyway.ApplicationContextAwareSpringJdbcMigrationResolver;
import org.flywaydb.core.internal.resolver.sql.SqlMigrationResolver;
import org.flywaydb.core.internal.util.Location;
import org.flywaydb.core.internal.util.PlaceholderReplacer;
import org.flywaydb.core.internal.util.scanner.Scanner;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;

import javax.sql.DataSource;
import java.sql.SQLException;

@Configuration
@ComponentScan("db.migration")
public class FlywayConfiguration {

    @Bean
    public BeanPostProcessor postProcessFlyway(ApplicationContext context) {
        return new BeanPostProcessor() {

            @Override
            public Object postProcessBeforeInitialization(Object o, String s) throws BeansException {
                return o;
            }

            @Override
            public Object postProcessAfterInitialization(Object o, String s) throws BeansException {
                if (o instanceof Flyway) {
                    Flyway flyway = (Flyway) o;
                    flyway.setSkipDefaultResolvers(true);
                    ApplicationContextAwareSpringJdbcMigrationResolver resolver = new ApplicationContextAwareSpringJdbcMigrationResolver(
                            new Scanner(Thread.currentThread().getContextClassLoader()),
                            new Location("classpath:db/migration"),
                            context.getBean(org.flywaydb.core.api.configuration.FlywayConfiguration.class),
                            context);
                    SqlMigrationResolver sqlMigrationResolver = null;
                    try {
                        sqlMigrationResolver = new SqlMigrationResolver(
                                getDbSupport(),
                                new Scanner(Thread.currentThread().getContextClassLoader()),
                                new Location("classpath:db/migration"),
                                PlaceholderReplacer.NO_PLACEHOLDERS,
                                "UTF-8",
                                "V",
                                "R",
                                "__",
                                ".sql");
                    } catch (SQLException e) {
                        e.printStackTrace();
                    }
                    flyway.setResolvers(sqlMigrationResolver, resolver);
                }
                return o;
            }

            private DbSupport getDbSupport() throws SQLException {
                DataSource dataSource = context.getBean(DataSource.class);
                if( ((org.apache.tomcat.jdbc.pool.DataSource)dataSource).getDriverClassName().equals("org.h2.Driver"))
                {
                    return new H2DbSupport(dataSource.getConnection());
                }
                else
                {
                    return new MySQLDbSupport(dataSource.getConnection());
                }
            }
        };
    }
}

请注意，我在tomcat jdbc pool，h2和mysql上有一些硬编码依赖项。如果你正在使用别的东西，你需要在那里更改代码（如果有人知道如何避免它，请发表评论！）

另请注意，@ComponentScan包需要与放置Java迁移类的位置相匹配。

另请注意，我必须重新添加SqlMigrationResolver，因为我想支持迁移的SQL和Java风格。

3）在执行实际迁移的db.migrations包中创建一个Java类：

@Component
public class V2__add_default_surveys implements SpringJdbcMigration {

    private final SurveyRepository surveyRepository;

    @Autowired
    public V2__add_surveys(SurveyRepository surveyRepository) {
        this.surveyRepository = surveyRepository;
    }

    @Override
    public void migrate(JdbcTemplate jdbcTemplate) throws Exception {
        surveyRepository.save(...);
    }
}

请注意，您需要将班级设为@Component，并且需要实施SpringJdbcMigration。在这个类中，您可以对您可能需要进行迁移的上下文中的任何Spring bean使用Spring构造函数注入。

注意：请务必禁用Hibernate的ddl验证，因为验证似乎在Flyway运行之前运行：

spring.jpa.hibernate.ddl-auto=none

Answer 3

如果您正在使用deltaspike，您可以使用BeanProvider获取对Class的引用。这是一个DAO示例，但它也适用于您的类。

更改您的DAO代码：

public static UserDao getInstance() {
    return BeanProvider.getContextualReference(UserDao.class, false, new DaoLiteral());
}

然后在您的迁移方法中：

UserDao userdao = UserDao.getInstance();

你有参考资料。

（引自：Flyway Migration with java）

Answer 4

简而言之，不要在您的数据库迁移中自动装配bean，甚至不要从应用程序中引用类！ 如果您重构/删除/更改在迁移中引用的类，它甚至可能无法编译甚至更糟地破坏您的迁移。

使用纯JDBC模板进行迁移的开销不值得冒险。